Transcription of Introduction to OFDM
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1E225C Lecture 16 OFDM IntroductionEE225 CEE225 CIntroduction to OFDMlBasic idea Using a large number of parallel narrow-band sub-carriers instead of a single wide-band carrier to transport informationlAdvantages Very easy and efficient in dealing with multi-path Robust again narrow-band interferencelDisadvantages Sensitive to frequency offset and phase noise Peak-to-average problem reduces the power efficiency of RF amplifier at the transmitterlAdopted for various standards DSL, , DAB, DVB2 Multipath can be described in two domains: time and frequencytimetimeSinusoidal signal as inputtimetimeSinusoidal signal as outputfFrequency responseTime domain: Impulse responseFrequency domain: Frequency responsetimeImpulse responsetimetimeModulationtechniques: monocarrier vs.
OFDM Modulation and Demodulation using FFTs b0 b1 b2.... bN-1 Data coded in frequency domain: one symbol at a time IFFT Inverse fast Fourier transform Data in time domain: one symbol at a time d0 d1 d2 d3.... dN-1 time f P/S Parallel to serial converter Transmit time-domain samples of one symbol d0, d1, d2, …., dN-1 Receive time -domain ...
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